Replaceable Tank Lining

ABSTRACT

Replaceable tank (RT) for installing in metallic storage tanks for fluids consists of a tank body and one or more orificial members. The RT conforms with inner walls of the storage tank and is made of flexible materials, such as rubber or PVC that are impermeable to the fluids stored. Orificial members having a tubular neck and conforming with the lumen of the orifices of the storage tank are typically made of the same material as the RT. Magnets, attached to, or embedded in, the walls of the RT are attracted to the walls of the metallic storage tank. A method for manufacturing, packaging and for in situ installing an RT is provided.

FIELD OF THE INVENTION

The present invention relates to storage tanks, and more particularly toa method for prolonging the durability of such tanks.

BACKGROUND OF THE INVENTION

Tanks used for storing petroleum and petrochemicals are normallydesigned to be leak resistant in order to minimize loss of theircontents in or onto the ground, which in excess amounts mightcontaminate the soil and pollute the surroundings. Many states haveenacted laws or regulations to protect the environment by enforcingrestrictions on the use of such tanks. Accordingly, operators or ownersof tanks storing petroleum, chemicals, or hazardous material, are toprovide secondary containment vessels. Secondary vessels such as anexterior shell or leak-proof housing are intended to surround thestorage tank and serve as a backup safety vessel to contain anymaterials which may leak out of the primary tank. In an effort to complywith these secondary containment laws and regulations, operative tanksare typically replaced by double walled tanks. A typical solution oftenapplied with regard to underground storage tanks includes encasing theexisting storage tanks (usually steel tanks) in concrete. Another commonsolution consists of placing an exterior liner or flexible bag around anexisting storage tank. Such techniques require excavation of the tanksites, or replacement, or reinstallation of the tanks, along withadditional construction.

U.S. Pat. No. 4,763,805 discloses a system which is suitable forinstallation especially in underground storage tanks. The system has anexpandable compartment such as a bladder which is made of a flexiblematerial like rubber that is impermeable to the stored fluids. Theexpandable compartment serves as a primary container, whereas theoperative tank encasing it serves as a secondary tank. However, thewalls of the expandable tank are prone to damage due to the dynamicallychanging volume of the space between the inner tank and the storagetank. Furthermore, installing such a tank is somewhat complex and mayrequire a presence of a worker inside the storage tank.

The present invention facilitates protection of the environment fromfaulty tanks, and is applicable especially to tanks attractive tomagnets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a longitudinal sectional view of a replaceable tank accordingto the invention;

FIG. 1B is a side view of the replaceable tank of FIG. 1A;

FIG. 1C is an isometric view of an orificial member of a replaceabletank according to a preferred embodiment of the present invention;

FIG. 2A is a frontal view of the replaceable tank of FIG. 1A after astep of flattening;

FIG. 2B is a frontal view of a section of a replaceable tank which ispartially folded;

FIG. 2C is a schematic presentation of a replaceable tank after a stepof folding;

FIG. 2D is a schematic presentation of a step of packaging a replaceabletank in a hollow cylinder according to a preferred embodiment of thepresent invention;

FIG. 3 is a schematic presentation of an insertion of a replaceable tankinto an operative tank according to a preferred embodiment of thepresent invention;

FIG. 4 is an isometric view of a jig for drilling an aperture in areplaceable tank of the invention;

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Containers or tanks made of a magnetic metal such as steel are oftenused for storing fluids considered contaminating and/or hazardous suchas fuel, oil, chemicals, pressurized propane or natural gas. Thesecontainers must not undergo deterioration that would promote leakage ofthe contents into the environment. The present invention provides amethod and system for applying an internal lining to such containers,with the intention of preventing leakage from the tank. Accordingly,replaceable tanks (RT) conforming to the internal contours of the metaltank of the art are provided. The RTs of the invention in effect providean internal, replaceable coating to the metal tank. An aged RT isreplaceable by a new one so that the external, metal tank is may corrodeor undergo other structural deterioration without the risk ofenvironmental damage by spillage of the contents. The RT of theinvention is made of flexible materials such as rubber or PVC,impermeable to the relevant fluids.

General Structure of the Replaceable Tank

Reference is first made to FIGS. 1A and 1B in which a longitudinalsectional view and a side view of a RT of the invention are shownrespectively. RT 10 has orifices 12 and 13 located at its top side.Magnets 14 are attached to the inner surface of the RT walls. Thedistances between magnets 14 are determined in respect of the weight ofthe empty RT and the intensity of the magnetic field which they induce.Side wall 16 is planar or dome shaped conforming to the internal shapeof the metal tank. Circumferential flange 17 provides for attachingtubular neck 18 to the rim of the corresponding orifices of the metaltank.

Typically a metal storage tank such as a fuel tank in a refuelingservice station has at least four orifices for performing the followingfunctions respectively: (i) filling the tank with fuel; (ii) dispensingfuel; (iii) measuring the level of the fuel; and (iv) a vent. The ventis the most narrow orifice of the lot, typically measuring acircumference of 1 inch. The widest orifice of the storage tank istypically used for the insertion of the RT into the tank for providinginternal lining.

Construction and Fitting of the RT

The construction of a RT is carried out in two main stages. At stage 1,the tank body and appendages are assembled, and at stage 2 the RT isfitted into the operative tank, typically in situ, and completed. A RTis produced from sheets of impermeable matter, for example rubber or PVCusually approximately 2 mm thick. The sheets are cut into smaller sheetsor pieces having a particular shape as required to assemble the RT.Then, the sheets and pieces of building material are joined by solderingor gluing such that the RT formed may fit in with the internal contoursof the metal tank. Magnets are attached or embedded in the inner surfaceof the RT typically prior to its assembly.

Typically a RT is assembled having at least one wide aperture located incorrespondence with the exact location of the orifice in the metal tank.A prior knowledge of the exact locations of the other apertures of themetal tank is not necessary for the assembling of a corresponding RT.Such additional apertures are made at the site of application. Anorificial member having a neck is inserted in conformity with anaperture, the procedure described with reference to FIG. 1C. Orificialmember 20 has a circumferential flange 22 located at one end of hollowtubular neck 24 and an external circumferential ridge 26 located at asecond end of the neck. Whether attached to the RT or not, the role ofthe ring is to prevent falling off or pulling away of the orificialmember. The external diameter and the length of the tubular neck fit inthe corresponding dimensions of an orifice of the metal tank. Holes 28provide for securing flange 22 to a rim of the corresponding orificialof the metal tank by means of bolts. A circular aperture matching theexternal diameter of the tubular neck is provided by punching, drilling,or cutting the corresponding piece of building materials used in theassembly of the RT prior to its assembly. After the assembly iscompleted the orificial member is inserted into this aperture such thatits circumferential ridge is pushed over to the other side of the rim ofthe aperture. The cylindrical neck is optionally further glued and orsoldered to the body of the RT. Other orificial members are produced inadvance, corresponding to the additional orifices of the metal tank.Orifices of the storage tank may vary in shapes, and therefore maydiffer from the cylindrical shape as described hereinabove. The shapesof the orificial members conform to the internal contours of thecorresponding orifices of the metal tank according to the presentinvention. The external ridge can also be segmented and the number ofsegments and/or the dimensions may vary. Rigid orificial members arepartially or completely made of rigid materials such as metals. Ingeneral, an orificial member for an orifice of a metal tank has acircumferential flange at one end and an external ridge at its other endof the tubular neck. The hollow tubular neck conforms to the innerdimensions of the metal orifice. For the sake of simplicity, thefollowing description of the invention refers to cases of cylindricalsymmetry wherein any one who is knowledgeable with the art is able toadopt the description to other geometrical shapes of orifices of suchstorage tanks.

Folding Up and Packaging a RT

RTs are packaged according to the invention for shipping to the site ofinstallation. Such packaging provides the background for a convenientinstallation process and is also convenient with regards to shipping. Aprocess of packaging consists of several steps: Firstly, the RT isflattened forming a planar geometrical body. Then the flattened RT isfolded and ropes are tied to its folded orificial members. Then, thefolded RT is twisted and packaged for shipping. Reference is now made toFIGS. 2A-2D in which several views of the RT at different stages of apackaging process according to a preferred embodiment of the presentinvention are correspondingly shown. In FIG. 2A a frontal view of aflattened, pre-folded RT of FIG. 1A is shown. In FIG. 2B a frontal viewof a section of the same RT, partially folded, is shown. In FIG. 2C aschematic presentation of same RT, completely folded, is shown. Fullyfolded RT 36 has orificial members 38 located at its topside folded aswell. At this stage a rope, not shown, is tied to each folded orificialmember to enable subsequent pulling out of the corresponding orifice ofthe metal tank as is described infra. Twisting of the folded RT iscarried out by rotating the upper and lower ends of RT 36 in opposingdirections around axis 42 as is indicated by arrows 42A and 42Bcorrespondingly. In FIG. 2D a packaged, folded and twisted RT isschematically shown. RT 46 is inserted into hollow cylinder 48 such thatfolded orificial members 50 and ropes 52 tied to them are the last to beinserted. The length of each of ropes 52 is not smaller than the heightof hollow cylinder 48. The free ends of these ropes are further securedto the inner wall of the hollow cylinder near its upper end. Lids, notshown, optionally cover the two orifices of hollow cylinder 48 after thefolded and twisted RT, folded orificial members 50 and ropes 52 arecompletely inserted into cylinder 48. The external radius of cylinder 48is smaller than the inner radius of the corresponding main orifice ofthe metal tank. The width of the wall of cylinder 48 which is made ofstandard packaging material such as cardboard or plastic sustains thestresses applied by the twisted RT and protects the RT from beingdamaged during shipment and/or storage. Optionally the inner surface ofhollow cylinder 48 is coated with a lubricant such as a talcum powderwhich does not harm the RT. Orificial members, intended for otherorifices of the metal tank and are made of flexible materials, aresimilarly packaged in corresponding cylinders.

The shape of the package need not be cylindrical. Any shape that fits inwith the shape of the corresponding orifice of the metal tank, such thatthe packaged RT, or the orificial members, can be inserted into thecorresponding orifices, is acceptable. Nevertheless the packaging isconstructed such that it is removable from the RT, or the orificialmembers, after the package is inserted into the interior of the metaltank.

Installing the RT

First the metal tank is emptied, any existing sediments are removed andthe inner surface of the tank is rinsed and cleaned. A thorough cleaningsuch as by chemical solvents, detergents and/or steam, is particularlyrequired in a periphery of any edges or sharp bulges that may damage theRT. Such surfaces optionally require further smoothing. Such smoothingcan be carried out by inner surface coating of the metal tank withplaster or sprayed with a foamy plastic resin. The RT can then beinserted into the metal tank through its main orifice.

Reference is now made to FIG. 3 in which a schematic presentation of aRT being inserted into a storage tank is shown. Storage tank 70 has amain orifice 72 through which the packaged RT is inserted. Hollowcylinder 74 in which the RT is packaged is pulled upwards from mainorifice 72 while RT 76 is forced downwards. The ropes, not shown, whichare tied to the orificial members of the RT are released at this stagefrom the upper end of the cylinder and are manually held while cylinder74 is completely removed from the RT. Twisted RT 76 is released and ispartially unfolded by the elastic forces applied by its deformed wallsand by gravity. The releasing and unfolding are manually assisted byshaking and rotating the ropes.

The process of fitting the orifices of the RT to the correspondingorifices of the metal tank is described in the following. If the RT hasmore than one orifice, the rope tied to each orificial member other thanthe orificial member corresponding to the main orifice of the metaltank, is pulled out of its corresponding orifice of the metal tank.Pulling the ropes tied to such different orificial members is effectedby means of a catching device. Such a catching device is inserted intothe metal tank through the corresponding orifice. Each of the orificialmembers is untied and unfolded and further pulled upwards through thecorresponding orifice of the metal tank. The circumferential flange ofan orificial member is rotated around its axis so that the topside wallof the RT is straitened. By means of such rotations the topside of theRT and all its assembled orificial members fit in the correspondingportion of the lumen of the metal tank. The flanges of all orificialmembers are secured to the rim of their corresponding orifices of themetal tank by bolts. Then, all other orificial members other than theone corresponding to the main orifice are sealed off. The RT is inflatedby pressurizing gas such as air through the main orifice. Keeping the RTpressurized for a predetermined time at a predetermined pressurecompletely untwines and unfolds the RT and further attaches it to theinner walls of the metal tank by means of the magnetic pieces. The RTremains attached to the inner walls of the metal tank conforming to itslumen even after being depressurized.

At this stage, installation of all the orificial members not yetinstalled is completed. Orifice 84 is an exemplary orifice thatcorresponds to either a wide orifice in which a corresponding orificialmember has not been installed during the stage of assembling a RT, oranother orifice such as an orifice for measuring the level of the fluidwhich is different from a vent. Venting orifices such as orifice 85typically have pipe 86 extending upwards of which one of its ends isconnected to the topside of the metal tank and other end 88 is curveddownwards.

An installation process of orificial members is carried out preferablyas herein described. First an aperture is made by drilling or punchingor cutting the top side wall of the RT which is attached to the innerwalls of the metal tank. The cover of the metal orifice is removed priorto that. In a case in which the metal orifice is a vent, a section ofthe pipe having its curved end is removed prior to cutting. Cutting suchas by drilling is effected through the corresponding orifice of themetal tank by employing a corresponding jig. The packaged orificialmember is inserted into the aperture drilled in the topside of the RT.Insertion of an orificial member is similarly carried out as theinsertion of the RT as described herein above. The cylinder in which thecorresponding orificial member is packaged is inserted into the metalorifice so that its open bottom end protrudes into the lumen of the RT.The packaged orificial member is pushed down, and concomitantly thecylinder is pulled up to completely remove it from the correspondingorifice of the metal tank. Then the twist of the orificial member isreleased further unfolding by elastic forces applied by its deformedwalls. In the case of a rigid orificial member, the lower end to beinserted in the metal tank is squeezed, before forcing into the orificeof the metal tank. A slight upward pulling attaches the circumferentialridge of both types of orificial members to the rim of the aperture cutin the topside wall of the RT. Then fitting the orificial member to themetal orifice of the tank is similarly carried out as describedhereinabove. After bolting the circumferential flanges of the orificialmembers to the rim of the metal orifices the covers of correspondingorifices are replaced and or the sections of a pipe having a curved endof a vent are reattached to the rim of the pipes fitted with thecorresponding orificial members.

Reference is now made to FIG. 4 in which an isometric view of anexemplary jig according to the invention is shown. Jig 100 has tubularguide 102 having cylindrical lumen and circular aperture 103. The innerdiameter of tubular guide 102 is slightly larger than the diameter ofthe drill to be employed. The diameter of circular flange 104 at the topof tubular guide 102 exceeds the diameter of the metal orifice to whichit is to be attached. Neck 106 has a diameter that closely reaches theinner diameter of the metal orifice. The bottom of the wall of tubularguide 108 is beveled so that its external lower diameter slightlyexceeds the inner diameter of its lumen. Such a jig is inserted into ametal orifice so that its tipped end is placed on top of the surface ofthe RT and its neck 106 fits in the rim of the metal orifice of themetal tank. By means of such a jig the aperture formed in the RT bydrilling through the jig is aligned with the orifice of the metal tank.Optionally after drilling a first hole in the upper wall of the RTthrough the lumen of such a jig, the hole is widened by means ofadditional drilling through this hole employing a drill whose diameteris slightly smaller than the diameter of the metal orifice and is largerthan the diameter of the first drill.

An aged RT need not be removed from an operative metal tank prior toreplacing. A new RT may be installed in a tank supplemented with a RT ofthe invention, much in the same way as described above. The metal tankfurnished with the additional new RT would thereby be converted to amulti-walled tank by such internal lining with the new RT. Obviously thenew RT slightly differs from the old one previously installed.

1. A replaceable tank (RT) for installing in a metallic storage tank forfluids, comprising: a tank body made of a flexible material impermeableto said fluids; at least one orificial member attachable to a hole insaid tank body, and at least one magnet attached to said tank body forattracting to said metallic storage tank.
 2. A RT for installing in astorage tank for fluids as in claims 1, wherein one end of a tubularneck of said at least one orificial member has an external ridge.
 3. ART for installing in a metallic storage tank for fluids as in claim 1,wherein said at least one orificial member is attached to said tankbody.
 4. A RT for installing in a metallic storage tank for fluids as inclaim 1, wherein one end of a tubular neck of said at least oneorificial member has a flange.
 5. A RT for installing in a metallicstorage tank for fluids as in claim 1, wherein said at least oneorificial member is rigid.
 6. A method for preventing leakage from metalstorage tanks comprising providing an internal lining to said storagetank by magnetically attaching a replaceable tank (RT) conforming to theinternal contours of the metal tank.
 7. A method for preventing leakagefrom metal storage tanks as in claim 6, wherein at least one orificialmember is further attached to said RT.
 8. A method for preventingleakage from metal storage tanks as in claim 6, further comprisingfolding said RT prior to shipping to the place of installation, andpackaging said folded RT in a package insertable into said storage tankthrough an orifice of said storage tank.
 9. A method for preventingleakage from metal storage tanks as in claim 6, wherein gas pressurizingis used for providing said lining,